Not applicable.
This invention relates to a generically well known process variously called xe2x80x9cphosphatingxe2x80x9d, xe2x80x9cphosphatizingxe2x80x9d, or xe2x80x9cphosphate conversion coatingxe2x80x9d in which a metallic substrate is coated with an adherent coating containing phosphate anions and metal cations, at least some of these metal cations being those corresponding to one or more metallic constituent(s) of the substrate. If the phosphating composition also contains divalent cations that can form only sparingly water-soluble phosphates, the conversion coating formed also normally includes some of these divalent cations from the phosphating composition.
Normally, a phosphate coating is formed by chemical reaction between the metal substrate and an aqueous liquid variously called a xe2x80x9cphosphatingxe2x80x9d or xe2x80x9cphosphatizingxe2x80x9d composition, solution, bath, or a like term; in some instances, the formation of the coating may be aided by, or even completely dependent on, application of an electric current. If the phosphating composition is in contact with the substrate for at least about five seconds at a temperature not more than 70xc2x0 C. and any liquid phosphating composition remaining in contact with the conversion coating thus formed is rinsed off before the substrate treated with it is dried, the phosphate coating formed generally is microcrystal line, particularly if the substrate and/or the phosphating composition contains substantial amounts of iron and/or zinc. If the phosphating composition is applied to the substrate and dried in place without rinsing, the coating formed is usually predominantly amorphous.
The presence of a phosphate coating on a metal substrate normally serves one or both of two major functions: (1) increasing the corrosion resistance of the substrate by comparison with an otherwise identical metal substrate that has no such conversion coating, an increase that may be measured either with or without a subsequent paint or similar protective coating and (2) serving as a strongly adherent xe2x80x9ccarrierxe2x80x9d for an externally applied lubricant material that facilitates mechanical cold working.
A major object of this invention is to achieve an additional benefit from a phosphate conversion coating in an operation of the former type when the phosphating composition is dried into place without rinsing. The specific benefit achieved is improved adhesion to subsequently applied paint, elastomers, sealants, and like coatings and adhered structural members, particularly when the conversion coated object that has been painted or adhered to an elastomeric and/or sealant type structural member is to be mechanically deformed after having been thus painted or adhered. (A xe2x80x9csealantxe2x80x9d may be defined for purposes of this description as an elastomeric material that serves at least one of the uses of (i) forming a load-bearing joint, (ii) excluding dust, dirt, moisture, and other chemicals that include a liquid or gas, (iii) reducing noise and vibrations, (iv) insulating, and (v) filling spaces). Other more detailed objects of the invention will become apparent from the description below.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word xe2x80x9caboutxe2x80x9d in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout the description, unless expressly stated to the contrary: percent, xe2x80x9cparts ofxe2x80x9d, and ratio values are by weight or mass; the term xe2x80x9cpolymerxe2x80x9d includes xe2x80x9coligomerxe2x80x9d, xe2x80x9ccopolymerxe2x80x9d, xe2x80x9cterpolymerxe2x80x9d and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ within the composition by chemical reaction(s) noted in the specification between one or more newly added constituents and one or more constituents already present in the composition when the other constituents are added, and does not preclude unspecified chemical interactions among the constituents of a mixture once mixed; specification of constituents in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole and for any substance added to the composition; any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to an object of the invention; the word xe2x80x9cmolexe2x80x9d means xe2x80x9cgram molexe2x80x9d, and the word itself and all of its grammatical variations may be used for any chemical species defined by all of the types and numbers of atoms present in it, irrespective of whether the species is ionic, neutral, unstable, hypothetical, or in fact a stable neutral substance with well defined molecules; an abbreviation once defined may be used thereafter with either exactly the same meaning or a grammatically varied meaning as indicated by the context and is to be understood as having the same meaning, Mutatis mutandis, as when first defined; the term xe2x80x9cpaintxe2x80x9d and its grammatical variations are to be understood as including any material or process that may be known by a more specialized term, such as xe2x80x9cenamelxe2x80x9d, xe2x80x9cvarnishxe2x80x9d, xe2x80x9clacquerxe2x80x9d, xe2x80x9cshellacxe2x80x9d, xe2x80x9celectropaintxe2x80x9d, xe2x80x9ctop coatxe2x80x9d, xe2x80x9cclear coatxe2x80x9d, xe2x80x9ccolor coatxe2x80x9d, xe2x80x9cautodeposited coatingxe2x80x9d, xe2x80x9cradiation curable coatingxe2x80x9d, xe2x80x9csiccative coatingxe2x80x9d, and the like and their grammatical variations; and the terms xe2x80x9csolutionxe2x80x9d, xe2x80x9csolublexe2x80x9d, xe2x80x9chomogeneousxe2x80x9d, and the like are to be understood as including not only true equilibrium solutions or homogeneity but also dispersions that show no visually detectable tendency toward phase separation over a period of observation of at least 100, or preferably at least 1000, hours during which the material is mechanically undisturbed and the temperature of the material is maintained within the range of 18-25xc2x0 C.
It has been found that the above stated object of the invention can be achieved by combining an adhesion-promoting substance with a conventional liquid phosphating composition. Specific embodiments of the invention include phosphating compositions containing one or more types of adhesion-promoting substances; processes for forming a phosphate conversion coating on a metal substrate by forming a liquid coating of an aqueous solution containing ingredients of a conventional phosphating composition and an adhesion-promoting substance over the metal substrate, and then drying the liquid layer in place on the metal substrate, without rinsing off any of the liquid layer with additional water and without any need for application of electromotive force from an external source; articles of manufacture including surfaces treated by such a process; and/or surfaces having a phosphate conversion coating that includes an adhesion-promoting substance and/or a product formed by drying an adhesion-promoting substance.
Non-exclusive examples of conventional phosphating compositions suitable for combining with at least one film-forming organic substance to produce a composition according to this invention include those described in the following U.S. Patents and applications therefor, the entire disclosures of which, except to any extent that they may be inconsistent with any explicit statement herein or with other more recently developed knowledge in the art, are hereby incorporated herein by reference: U.S. National application Ser. Nos. 08/344,829; 08/464,609; 08/569,177, now abandoned; 08/638,268, now abandoned; 60/036,606, now abandoned; and 08/849,704, now abandoned; PCT Application Nos. US96/19144; and US96/02677; and U.S. Pat. Nos. 5,900,073; 5,891,268; 5,776,265; 5,645,650; 5,683,816; 5595,611; 5,498,300; 5,472,522; 5,451,271; 5,378,292; 5,261,973; 5,143,552; 5,125,989; 5,082,511; 5,073,196; 5.045,130; 5,000,799; 4,992,116; 4,961,794; 4,927,472; 4,880,467; 4,874,480; 4,849,031; 4,722,753; 4,717,431; 4,673,444; 4,643,778; 4,639,295; 4,637,838; 4,612,060; 4,596,607; 4,595,424; 4,565,585; 4,559,087; 4,539,051; 4,529,451; 4,517,029; 4,515,643; 4,486,241; 4,443,273; 4,419,199; 4,419,147; 4,416,705; 4,402,765; 4,385,096; 4,377,487; 4,338,141; 4,311,535; 4,292,096; 4,289,546; 4,265,677; 4,220,486; 4,142,917; 4,108,690; 4,063,968; 3,939,014; 3,932,287; 3,870,573; 3,860,455; 3,850,700; 3,839,099; 3,795,548; 3,758,349; 3,723,334; 3,723,192; 3,706,604; 3,697,332; 3,671,332; 3,645,797; 3,619,300; 3,615,912; 3,607,453; 3,573,997; 3,565,699; 3,547,711; 3,533,859; 3,525,651; 3,519,495; 3,519,494; 3,516,875; 3,515,600; 3,493,400; 3,484,304; Re 27,896; 3,467,589; 3,454,483; 3,450,579; 3,450,578; 3,450,577; 3,449,222; 3,444,007; 3,401,065; 3,397,093; 3,397,092; 3,380,859; 3,338,755; 3,297,493; 3,294,593; 3,268,367; 3,240,633; 3,218,200; 3.197,344; 3,161,549; 3,154,438; 3,146,133; 3,133,005; 3,101,286; 3,046,165; 3,015,594; 3,007,817; 2,979,430; 2,891,884; 2,882,189; 2,875,111; 2,840,498; 2,835,618; 2,835,617; 2,832,707; 2,819,193; 2,813,814; 2,813,813; 2,813,812; 2,798,829; 2,758,949; 2,744,555; 2,743,204; 2,724,668; 2,702,768; 2,665,231; 2,657,156; 2,609,308; 2,591,479, 2,564,864; 2,540,314; 2,298,312; 2,298,280; 2,245,609; 2,132,883; 2,121,574; 2,121,520; 2,120,212; 2,114,151; 2,076,869; 1,660,661; 1,654,716; 1,651,694; 1,639,694; 1,610,362; 1,485,025; 1.388,325; 1,377,174; 1,341,100; 1,320,734; 1,317,351; 1,292,352; 1,290,476; 1,287,605; 1,254,264; 1,254,263; 1,248,053; 1,219,526; 1,215,463; and 1,206,075.
Because a liquid composition according to this invention is applied by the dry-in-place method, the concentration of the various ingredients in it has relatively little effect by itself on the quality of the protection obtained, which instead depends more on the total amount of the active ingredients put into place on each unit area of the surface, the ratios among the active ingredients, and the time and temperature of drying. Accordingly, the preferred concentrations will be described below primarily in terms of ratios between ingredients. However, preferred concentrations in working compositions are given for one ingredient; these preferences are primarily for practical convenience in supplying the desired total amounts of the active, non-volatile ingredients of the compositions.
A composition according to the invention must contain phosphate anions. They may be supplied to the composition by any oxyacid of phosphorus, or water-soluble salt thereof, in which the phosphorus is in its +5 valence state, i.e., orthophosphoric acid, metaphosphoric acid, and the condensed phosphoric acids corresponding to the general formula H(n+2)PnO(3n+1), where n represents a positive integer with a value of at least 2. As is generally known in the art, these species are all believed to exist in equilibrium with one another, with the equilibrium strongly favoring orthophosphoric acid and/or its salts at low temperatures and concentrations and favoring the more condensed acids, including metaphosphoric acid, and/or their salts at higher temperatures and concentrations. At least for reasons of economy, simple orthophosphoric acid, for which the chemical formula is H3PO4, and/or at least one salt thereof, is normally preferred as the source for the phosphate ions in a composition according to this invention. The concentration of phosphate ions in a working composition according to the invention, measured as its stoichiometric equivalent as orthophosphoric acid, preferably is at least, with increasing preference in the order given, 1.0, 2.0, 4, 6, 8, 11, 15, 20, 25, 30, 33, 36, 39, 41, 44, 47, 50, 53, 56, or 58 grams of orthophosphoric acid per liter of total working composition, a concentration unit that may be used hereinafter for any other constituent as well as for orthophosphoric acid and is hereinafter usually abbreviated as xe2x80x9cg/lxe2x80x9d, and, if the working composition according to the invention is to be used to form a phosphate coating to be adhered to an elastomer, this concentration of phosphate ions in a working composition according to the invention, measured as its stoichiometric equivalent as orthophosphoric acid, more preferably is at least, with increasing preference in the order given, 70, 80, 90, 100, 110, 120, 130, 140, 145, 150, 155, or 160 g/l. Independently, at least for economy, this concentration of phosphate ions in a working composition according to the invention, measured as its stoichiometric equivalent as orthophosphoric acid, preferably is not more than, with increasing preference in the order given, 400, 200, 190, 185, 180, 175, 170, or 165, g/l, and, unless the working composition according to the invention is being used to form a coating to be bonded to an elastomer, this concentration more preferably is not more than, with increasing preference in the order given, 140, 130, 120, 110, 105, 100, 95, 90, 85, 80, 75, 70, 65, or 60 g/l. In deciding whether a composition conforms to one of these preferences, the stoichiometric equivalent as orthophosphoric acid of all sources of pentavalent phosphorus dissolved in a composition according to the invention is to be considered present as orthophosphoric acid, irrespective of the actual extent of ionization, complex formation, condensed phosphate formation, or the like.
A working composition according to the invention also contains zinc cations, which may be supplied to the composition by dissolving therein any suitable zinc salt or a combination of acid and elemental zinc, zinc oxide, or zinc hydroxide. If a substrate being coated is predominantly elemental zinc, an adequate and even a preferred amount of zinc can be dissolved into the working composition from the substrate before the working composition dries. Normally, however, in order to avoid substantial variations in coating quality, it is preferred to provide zinc cations in a controlled concentration to the working composition before the latter is contacted with the substrate to be coated. For convenience, freedom from contaminants that can cause quality problems in the coatings formed, and economy, either zinc oxide or zinc dihydrogen phosphate is preferred as a source of zinc ions for a composition according to this invention. The total zinc content of any source of zinc cations thus explicitly supplied to the composition is to be understood hereinafter to be present as zinc cations, irrespective of the actual degree of ionization, complex formation, ion association, or the like that may prevail in the actual working composition.
In a working composition according to the invention, the concentration in g/l of zinc cations preferably has a ratio to the concentration of phosphate ions, measured as their stoichiometric equivalent in g/l as orthophosphoric acid, that is at least, with increasing preference in the order given, 0.003:1.00, 0.005:1.00, 0.007:1.00, 0.010:1.00, or 0.013:1.00. If the working composition is used to form a coating to be painted, the ratio defined in the immediately preceding sentence more preferably is at least, with increasing preference in the order given, 0.015:1.00, 0.020:1.00, 0.025:1.00, 0.029:1.00, or 0.033:1.00. Independently, in any working composition according to the invention, the ratio as described in the two immediately preceding sentences preferably is not more than, with increasing preference in the order given, 0.10:1.00, 0.08:1.00, 0.06:1.00, 0.055:1.00, 0.050:1.00, 0.045:1.00, 0.040:1.00, or 0.035:1.00.
A composition according to the invention preferably contains manganese cations. The most preferred source for these manganese cations is manganous oxide, which dissolves in acidic aqueous solutions to supply manganese cations. Independently of the source of the manganese cations, their concentration in g/l in a composition according to the invention preferably has a ratio to the concentration of phosphate ions, measured as their stoichiometric equivalent in g/l as orthophosphoric acid in the same composition that is at least, with increasing preference in the order given, 0.01:1.00, 0.030:1.00, 0.040:1.00, 0.045:1.00, 0.050:1.00, 0.055:1.00, 0.060:1.00, 0.065:1.00, 0.070:1.00, or 0.075:1.00. If the composition according to the invention is to be used to form a coating to be painted, the same manganese:phosphate ratio as defined in the preceding sentence more preferably is at least, with increasing preference in the order given, 0.080:1.00, 0.085:1.00, 0.090:1.00, or 0.095:1.00. Independently, at least for economy, this same manganese:phosphate ratio as described in the two immediately preceding sentences preferably is not more than, with increasing preference in the order given, 0.7:1.00, 0.5:1.00, 0.3:1.00, 0.20:1.00, 0.18:1.00, 0.16:1.00, 0.14:1.00, 0.12:1.00, or 0.10:1.00.
Independently, a composition according to the invention preferably contains nickel cations, the preferred source of which is nickel phosphate. Independently of their particular source, the concentration in g/l of nickel cations in a composition according to the invention preferably has a ratio to the concentration of phosphate ions, measured as their stoichiometric equivalent in g/l as orthophosphoric acid in the same composition, that is at least, with increasing preference in the order given, 0.003:1.00, 0.005:1.00, 0.007:1.00, 0.010:1.00, 0.015:1.00, 0.020:1.00, or 0.025:1.00. If the coating formed by the working composition is painted, the same nickel:phosphate ratio as defined in the immediately preceding sentence more preferably is at least 0.029:1.00 and still more preferably is at least 0.032:1.00. Independently, at least for economy, this nickel:phosphate ratio as described in the two immediately preceding sentences preferably is not more than, with increasing preference in the order given, 0.10:1.00, 0.080:1.00, 0.075:1.00, 0.070:1.00, 0.065:1.00, 0.060:1.00, or 0.055:1.00, and if the coating formed by the working composition is painted, this same nickel:phosphate ratio is more preferably not more than, with increasing preference in the order given, 0.050:1.00, 0.045:1.00, 0.040:1.00, or 0.035:1.00.
Independently, a composition according to the invention preferably contains at least one of (i) hydroxylamine, in free or bound form and (ii) iron cations. Any iron cations present preferably are predominantly in the ferrous oxidation state, inasmuch as ferrous phosphate is considerably more water soluble than ferric phosphate. Any iron salt or oxide, or even iron metal (which will dissolve in acidic solutions, accompanied by hydrogen gas evolution) may be used as the source; ferrous sulfate is most preferred for convenience and economy. (Also, in a concentrate composition, the amounts of sulfate introduced into the composition by adding preferred amounts of iron as iron sulfate are believed to have a positive effect on the storage stability of the concentrate composition.) Independently of their source, the concentration of iron cations when these cations are present preferably has a ratio to the concentration of phosphate ions, measured as their stoichiometric equivalent as orthophosphoric acid, in the same composition, all of these concentrations being measured in g/l, that is at least, with increasing preference in the order given, 0.0003:1.00, 0.0005:1.00, 0.0007:1.00, 0.0010:1.00, 0.0015:1.00, 0.0020:1.00, 0.0025:1.00, 0.0029:1.00, or 0.0032:1.00 and independently preferably is not more than, with increasing preference in the order given, 0.010:1.00, 0.008:1.00, 0.006:1.00, 0.0055:1.00, 0.0050:1.00, 0.0045:1.00, 0.0040:1.00, or 0.0035:1.00.
Instead of iron cations, hydroxylamine may be used at least equally preferably, the hydroxylamine having been observed to be very stable even in concentrate compositions according to the invention when supplied as at least one of its salts with a strong acid. Oximes can also serve as a suitable source of hydroxylamine. Hydroxylamine sulfate is most preferred for economy and because, as already noted, sulfate is believed to contribute to the storage stability of highly concentrated compositions according to the invention. Irrespective of the specific source, when hydroxylamine is used in a working composition according to this invention, its concentration, measured as its stoichiometric equivalent as hydroxylamine, preferably has a ratio to the concentration of phosphate ions measured as their stoichiometric equivalent as orthophosphoric acid, all of these concentrations being measured in g/l, that is at least, with increasing preference in the order given, 0.0010:1.00, 0.0020:1.00, 0.0030:1.00, 0.0040:1.00, 0.0045:1.00, 0.0050:1.00, 0.0054:1.00, or 0.0056:1.00 and independently, at least for economy, preferably is not more than, with increasing preference in the order given, 0.08:1.00, 0.05:1.00, 0.03:1.00, 0.0100:1.00, 0.0090:1.00, 0.0080:1.00, 0.0070:1.00, 0.0065:1.00, 0.0060:1.00, or 0.0058:1.00.
A composition according to the invention may contain any of the additional divalent cations cobalt, magnesium, calcium, copper, and the like, often found useful in conventional phosphating compositions. Any of these additional divalent cations, except copper, when used preferably is present within one of the preferred concentration ranges indicated above for nickel. If copper is used, it preferably is present in a concentration that is, with increasing preference in the order given, from 3 to 100, 6 to 75, or 13 to 30 milligrams of copper per liter of total composition.
At least if a process according to the invention is producing a coating to be bonded to a sealant or elastomer, the working composition used in preferably contains calcium cations in a concentration that has a ratio to the concentration of phosphate ions, measured as their stoichiometric equivalent as orthophosphoric acid, all of these concentrations being measured in g/l, that is at least, with increasing preference in the order given, 0.007:1.00, 0.010:1.00, 0.015:1.00, 0.020:1.00, 0.025:1.00, 0.030:1.00, 0.035:1.00, 0.040:1.00, 0.044:1.00, or 0.048:1.00 and independently preferably, at least for economy, is not more than, with increasing preference in the order given, 0.30:1.00, 0.20:1.00, 0.15:1.00, 0.10:1.00, 0.090:1.00, 0.080:1.00, 0.075:1.00, 0.070:1.00, 0.065:1.00, 0.060:1.00, 0.055:1.00, or 0.050:1.00.
As with conventional phosphating practice, when the substrates to be treated are predominantly zinciferous or similarly electrochemically active, no accelerator is generally needed in the conventional phosphating composition part of a composition according to the invention, while if the substrates are predominantly ferriferous, an accelerator may be advantageous, although not strictly required because the treatment is by drying in place. Adequate guidance as to suitable accelerators is provided by the prior phosphating art. For example, a dissolved accelerator component may consist of at least one of: 0.3 to 4 g/l of chlorate ions; 0.01 to 0.2 g/l of m-nitrobenzene sulfonate ions; 0.05 to 2 g/l of m-nitrobenzoate ions; 0.05 to 2 g/l of p-nitrophenol; 0.005 to 0.15 g/l of hydrogen peroxide in free or bound form; 0.1 to 10 g/l of hydroxylamine in free or bound form; and 0.1 to 10 g/l of a reducing sugar.
In addition to the above-considered ingredients of a conventional phosphating composition, a composition according to the invention must include at least one adhesion-promoting substance, which preferably is selected from the group consisting of (i) film-forming organic substances, (ii) polymers of vinyl phenols modified by substitution of substituted aminomethyl moieties on the aromatic rings of the polymers of vinyl phenols, as described in more detail in one or more of U.S. Pat. Nos. 5,891,952, 5,298,289, 5,266,410, 5,068,299, and 5,063,089, the entire disclosures of all of which, except for any part that may be inconsistent with any explicit statement herein, are hereby incorporated herein by reference, this type of polymers being hereinafter denoted briefly as xe2x80x9camino-phenolic polymersxe2x80x9d (these materials may be, but need not necessarily be, film-forming organic substances also), and (iii) inorganic oxides of one of the elements silicon, aluminum, titanium, and zirconium. A film-forming organic substance is defined for this purpose as an organic material that has all of the following properties:
when isolated from other materials, the film-forming organic substance is a solid at 30xc2x0 C. and normal atmospheric pressure;
the film-forming organic substance can be dissolved or stably dispersed in water to form a homogeneous solution in which the film-forming organic substance constitutes at least 5% of the homogeneous solution; and
when a homogeneous solution of the film-forming organic substance in water that contains at least 0.10 cubic centimeters volume of the isolated film-forming organic substance is dried at a temperature of 30xc2x0 C. in a walled container with a base area of 1.0 square centimeter and walls perpendicular to the base, there is formed in the base of said container a continuous solid article of the film-forming organic substance, said continuous solid article, after being separated from the container in which it was formed by drying, having sufficient cohesion to sustain its integrity against the force of natural gravity of the Earth.
Preferred film-forming organic substances for inclusion in a composition according to the invention used to form a phosphate coating to be painted are selected from the group consisting of synthetic polymers of monomers selected from the group consisting of acrylic and methacrylic acids, esters of acrylic and methacrylic acids, amides of acrylic and methacrylic acids, and nitrites of acrylic and methacrylic acids, this group being hereinafter denoted briefly as xe2x80x9cacrylic polymersxe2x80x9d.
Acrylic polymers to be used as an adhesion promoting additive in this invention still more preferably have a xe2x80x9cT300xe2x80x9d value, which is defined as the highest temperature at which an air-dried film of the polymer has a torsional modulus of at least 300 kilograms per square centimeter, that is at least, with increasing preference in the order given, 0, 5, 10, 15, 20, 25, 29, or 32xc2x0 C. and independently preferably is not more than, with increasing preference in the order given, 100, 75, 60, 50, 45, 41, 37, or 34xc2x0 C.
When a composition according to the invention contains a film-forming organic substance and/or at least one amino-phenolic polymer and is used to form a conversion coating to be painted, the concentration of these organic adhesion-promoting substances in g/l (on a basis of ultimate solids after drying) preferably has a ratio to the stoichiometric equivalent concentration of orthophosphoric acid in the same composition, also measured in g/l, that is at least, with increasing preference in the order given, 0.10:1.00, 0.30:1.00, 0.50:1.00, 0.60:1.00, 0.65:1.00, 0.70:1.00, 0.75:1.00, or 0.80:1.00 and independently preferably, at least for economy, is not more than, with increasing preference in the order given, 5:1.00, 3.0:1.00, 2.5:1.00, 2.0:1.00, 1.5:1.00, or 1.2:1.00, or, if the organic adhesion-promoting substance is a film-forming organic substance, 1.0:1.00.
Preferred amino-phenolic polymers for use in a composition according to the invention used to form a coating to be painted have at least one of the following characteristics, each of which is preferred independently of the others, and more preferably have more than one of the following characteristics, the preference being greater the greater the number of the following preferences included in it, polymers conforming to all of these preferences thus being the most preferred:
if all of the substituents on the aromatic rings that are substituted aminomethyl moieties and all of the substituents on the oxygen atoms bonded directly to the aromatic rings were replaced by hydrogen, the resulting polymer would be a polymer of a vinyl phenol, most preferably 4-vinyl phenol, and this polymer would have a weight average molecular weight that is at least, with increasing preference in the order given, 300, 400, 500, 600, 700, 800, 900, or 1000 and independently preferably is not more than, with increasing preference in the order given, 20,000, 15,000, 10,000, 9000, 8000, 7000, 6000, 5000, 4000, 3000, or 2000;
the nitrogen atoms in the substituted aminomethyl substituents on aromatic rings of the polymer molecules are preferably bonded to three distinct carbon atoms each, or in other words the amino moieties are tertiary amino moieties, and are not amine oxides;
at least one of the moieties bonded to each nitrogen atom in the substituted aminomethyl substituents on the aromatic rings is a poly hydroxy alkyl moiety conforming to the general formula xe2x80x94CH2xe2x80x94(CHOH)nxe2x80x94CH2OH, where n represents a positive integer, and the average value of nxe2x80x2, which is defined as the ratio of the number of hydroxyl moieties in all substituted aminomethyl substituents in the component of amino-phenolic polymers to the number of nitrogen atoms in all substituted aminomethyl substituents in the component of amino-phenolic polymers, is not less than, with increasing preference in the order given, 1.0, 2.0, 3.0, 3.5, 4.0, 4.5, or 4.9 and independently preferably is not more than, with increasing preference in the order given, 11, 9.0, 8.0, 7.5, 7.0, 6.5, 6.0, 5.5, or 5.1;
at least one of the moieties bonded to each nitrogen atom in the substituted aminomethyl substituents on the aromatic rings is an unsubstituted alkyl moiety having a number of carbon atoms that is not greater than, with increasing preference in the order given, 4, 3, 2, or 1.
Among the inorganic adhesion-promoting substances, silica is most preferred because it is most readily available commercially in suitable particle sizes already stably dispersed. When the adhesion-promoting substance is inorganic, its concentration in a composition according to the invention preferably has a ratio to the concentration of phosphate ions, expressed as its stoichiometric equivalent as orthophosphoric acid, that is at least, with increasing preference in the order given, 0.003:1.00, 0.005:1.00, 0.007:1.00, 0.009:1.00, 0.011:1.00, 0.013:1.00, or 0.015:1.00 and independently preferably, at least for economy, is not more than, with increasing preference in the order given, 1.00:1.00, 0.80:1.00, 0.70:1.00, 0.60:1.00, 0.50:1.00, 0.45:1.00, 0.43:1.00, 0.41:1.00, 0.39:1.00, or 0.37:1.00.
When a composition according to this invention is used to form a coating to be bonded to an elastomer, amino-phenolic polymers are preferred over acrylate polymers and inorganic material for the adhesion promoting additive, and when amino-phenolic polymers are used, their concentration in g/l (on a basis of ultimate solids after drying) preferably has a ratio to the phosphate ions concentration, measured as its stoichiometric equivalent of orthophosphoric acid in the same composition, also measured in g/l, that is at least, with increasing preference in the order given, 0.0005:1.00, 0.0010:1.00, 0.0020:1.0, 0.0024:1.00, 0.0027:1.00, 0.0030:1.00, 0.0032:1.00, 0.0034:1.00, 0.0036:1.00, or 0.0038:1.00 and independently preferably, at least for economy, is not more than, with increasing preference in the order given, 5:1.00, 3.0:1.00, 1.0:1.00, 0.50:1.00, 0.25:1.00, 0.10:1.00, 0.050:1.00, 0.020:1.00, 0.015:1.00, 0.010:1.00, 0.0090:1.00, 0.0080:1.00,0.0070:1.00, 0.0060:1.00, 0.0050:1.00, 0.0045:1.00, 0.0042:1.00, or 0.0040:1.00.
Preferred amino-phenolic polymers for use in a composition according to the invention used to form a coating to be adhered to elastomer have at least one of the following characteristics, each of which is preferred independently of the others, and more preferably have more than one of the following characteristics, the preference being greater the greater the number of the following preferences included in it, polymers conforming to all of these preferences thus being the most preferred:
if all of the substituents on the aromatic rings that are substituted aminomethyl moieties and all of the substituents on the oxygen atoms bonded directly to the aromatic rings were replaced by hydrogen, the resulting polymer would be a polymer of a vinyl phenol, most preferably 4-vinyl phenol, and this polymer would have a weight average molecular weight that is at least, with increasing preference in the order given, 300, 400, 500, 600, 700, 800, 900, or 1000 and independently preferably is not more than, with increasing preference in the order given, 20,000, 15,000, 10,000, 9000, 8000, 7000, 6000, 5000, 4000, 3000, or 2000;
the nitrogen atoms in the substituted aminomethyl substituents on aromatic rings of the polymer molecules are preferably bonded to three distinct carbon atoms each, or in other words the amino moieties are tertiary amino moieties, and are not amine oxides;
at least one of the moieties bonded to each nitrogen atom in the substituted aminomethyl substituents on the aromatic rings is a hydroxy, preferably a monohydroxy, alkyl moiety with a number of carbon atoms that preferably is at least two and independently preferably is not more than, with increasing preference in the order given, 6, 4, 3, or 2;
at least one of the moieties bonded to each nitrogen atom in the substituted aminomethyl substituents on the aromatic rings is an unsubstituted alkyl moiety having a number of carbon atoms that is not greater than, with increasing preference in the order given, 4, 3, 2, or 1.
A process according to this invention is performed by a dry-in-place method; i.e., a liquid layer of a composition according to the invention is formed over the substrate surface to be treated in the process and then dried into place without any intermediate rinsing, so that the entire non-volatiles content of the liquid layer initially formed, possibly modified by chemical reaction with the surface being treated, remains in place as the coating formed in a process according to the invention.
A working composition according to the invention may be applied to a metal work piece and dried thereon by any convenient method, several of which will be readily apparent to those skilled in the art. For example, coating the metal with a liquid film may be accomplished by immersing the surface in a container of the liquid composition, spraying the composition on the surface, coating the surface by passing it between upper and lower rollers with the lower roller immersed in a container of the liquid composition, and the like, or by a mixture of methods. Excessive amounts of the liquid composition that might otherwise remain on the surface prior to drying may be removed before drying by any convenient method, such as drainage under the influence of gravity, squeegees, passing between rolls, and the like. Drying also may be accomplished by any convenient method, such as forced hot air blowing, passage through a heated oven, infrared heating and the like.
For flat and particularly continuous flat workpieces such as sheet and coil stock, application by a roller set in any of several conventional arrangements, followed by drying in a separate stage, is generally preferred. The temperature during application of the liquid composition may be any temperature within the liquid range of the composition, although for convenience and economy in application by roller coating, normal room temperature, i.e., from 20-30xc2x0 C., is usually preferred. In most instances for continuous processing of coils, rapid operation is favored, and in such instances the most preferred drying is by infrared radiative heating, to produce a peak metal temperature that is at least, with increasing preference in the order given, 20, 30, 40, 50, 60, or 66xc2x0 C. and independently preferably is not more than, with increasing preference in the order given, 230, 220, 210, 200, 190, 180, or 177xc2x0 C. If the process is forming a coating to be bonded to elastomer, the peak metal temperature still more preferably is not more than, with increasing preference in the order given, 150, 125, 120, 115, 110, 105, 100, or 95xc2x0 C. Any other method of heating, for example a hot air oven, may be used, preferably to achieve the same peak metal temperature.
Alternatively, particularly if the shape of the substrate is not suitable for roll coating, a composition may be sprayed onto the surface of the substrate, which may optionally be preheated, and allowed to dry in place; such cycles can be repeated as often as needed until the desired amount of coating, generally measured in grams of coating per square meter of substrate surface coated (a unit of measurement hereinafter usually abbreviated as xe2x80x9cg/m2xe2x80x9d), is achieved. For this type of operation, the same peak metal temperatures as specified in the immediately preceding paragraph are preferred.
The amount of dry add-on mass per unit area of substrate surface treated (often alternatively called xe2x80x9ccoating weightxe2x80x9d) in a process according to the invention preferably is at least, with increasing preference in the order given, 0.05, 0.10, 0.15, 0.20, 0.24, 0.26, 0.28, 0.30, or 0.32 g/m2, or if the coating is to be adhered to elastomer still more preferably is at least, with increasing preference in the order given, 0.35, 0.40, 0.45, 0.50, or 0.53 g/m2. Independently, at least for economy, this coating weight preferably is not more than, with increasing preference in the order given, 8, 6, 5.0, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, or 1.2, and if the coating formed is to be painted and particularly if the substrate is intended to receive another conversion coating after being mechanically shaped subsequent to a process according to the invention, this coating weight still more preferably is not more than, with increasing preference in the order given, 1.00, 0.90, or 0.85 g/m2.
Preferably, a metal surface to be treated according to the invention is first cleaned of any contaminants, particularly organic contaminants and foreign metal fines and/or inclusions. Such cleaning may be accomplished by methods known to those skilled in the art and adapted to the particular type of metal substrate to be treated. For example, for galvanized steel surfaces, the substrate is most preferably cleaned with a conventional hot alkaline cleaner, then rinsed with hot water, squeegeed, and dried. For aluminum, the surface to be treated most preferably is first contacted with a conventional hot alkaline cleaner, then rinsed in hot water, then, optionally, contacted with a neutralizing acid rinse, before being contacted with a composition according to the invention as described above.